Evidence Collection and Crime Scene Investigation

Objective : Differentiate between the different types of evidence Do Now : Is blood evidence 100% conclusive?

Locard’s Exchange Principle “When a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur.”

Types of Evidence

1. Direct: firsthand observations (eyewitness account, video camera, confessions) shows that something is a fact without inference or presumption

Types of Evidence 2. Circumstantial: indirect evidence; implies a fact, but does not directly prove it requires making an inference Trace Evidence: a) Physical – bullets, weapons, impressions b) Biological – body fluids, plant parts, hair

Trace Evidence Small but measurable amounts of physical or biological material found at a crime scene

Examples of Trace Evidence Hair Fibers Soil fingerprints Body fluids (semen, blood, saliva, mucus) Paint chips Broken glass Chemical residue

Categories of Evidence Class Evidence Narrows identity to a group of persons or things Example: blood type Individual Evidence Narrow identity to a single person or thing Example: fingerprint

Your Task In your groups complete “Identifying types of evidence” activity.

Closure Identify what evidence you can collect at this scene State whether its biological or physical then state if its class or individual.

Objective: Problems with evidence collection Do Now: Can you convict someone on circumstantial evidence alone?

Case Study Complete the case study on OJ Simpson Closure: Do you agree or disagree with the OJ verdict?

Objective: Observe Locard’s Principle Do Now: What led to OJ Simpsons acquittal?

Complete the locard’s principle lab in your groups. Closure: Explain locard’s principle to me as if I was absent and didn’t know it.

Objective: how to process a crime scene Do Now: What was most useful in analyzing your data in your lab?

The Crime Scene Investigation Team Who is at the crime scene? Police and possibly a district attorney. Crime scene investigators. Medical examiners. Detectives. Specialists.

The Seven S’s of Crime Scene Investigation 1. Secure the scene. 2. Separate the witnesses. 3. Scan the scene. 4. See that photos are taken. 5. Sketch the scene. 6. Search for evidence. 7. Secure the collected evidence.

1. Secure the Scene

2. Separate the Witnesses Do not allow witnesses to talk to each other Witness accounts will be compared Avoid witnesses working together to create a story Asked: who, what, where?

3. Scan the scene Determine primary and secondary crime scenes Primary : where murder took place Secondary : where corpse was found Where should photos be taken? Wear protective gear to prevent contamination of crime scene

Marking Evidence

4. See that photos are taken Show the scene exactly as it was when you first saw it If something was moved before you arrived, don’t try to reconstruct the scene – just take the pictures the way you see it Be careful not to destroy any evidence while taking photos

Overall Shots – Outside the Scene Exit (door) First shot entering door: Outside science office

Overall Shots – Inside the Scene

Overall Shots – Outside the Scene Exit (door) First shot entering door: Outside science office

Overall Shots – Inside the Scene

Evidence: Knife (possible weapon) Midrange Photo Close-Up (with ruler)

5. Sketch the Crime Scene Make accurate rough sketch Note direction ( N) and scale of distance Include relevant objects (body, doors, windows, furniture, immovable landmarks) Make final copy for court

Rough sketch

Final Sketch

6. Search for evidence Grid, strip or lane, spiral search pattern Use flashlight to find hair and fibers Use forceps, vacuum cleaner to collect evidence GridStrip or LaneSpiral

7. Secure the Evidence Properly package, seal, and label ALL evidence! Liquid: airtight, unbreakable containers Wet items (biological): dry out in breathable container Dry item: bindle  plastic or paper container Seal with tape and labeled with pertinent info

The Chain of Custody In order to present credible evidence in court, a chain of custody log is essential. (in real life there is more involved but for this class do as follows) Bag evidence (seal, sign and date) Fill out evidence log every time you open it.

Rough Sketch Questions Using the rough sketch complete the questions.

Objective: Sketch a crime scene DO NOW: What happens if the chain of custody is broken for a piece of evidence?

Lab Sketching the Crime Scene In your groups complete the lab on sketching the crime scene. Divide up the work. Have some members: 1. Take measurements 2. Sketch